This proposal is to obtain financial support for a Symposium entitled "Phenotypic Variation in Populations: Relevance to Risk Assessment" that will take place December 7-10, 1986 at Brookhaven National Laboratory, and will be sponsored by the Biology and Medical Departments. We request funds for travel costs and registration fees for our invited speakers in the session Variations with Age; we also solicit five scholarships to enable graduate students and postdoctoral fellows to attend. We hope also to receive monetary support to defray the costs of running the Symposium. Risk assessment and the regulation of human exposure to mutagens, carcinogens, and teratogens is fraught with difficulties. Government agencies, industry, academia, and the law, rightly are concerned with the reduction of risk. The number of Symposia on risk assessment at its various levels from molecular biology to management practices, reflect these concerns and the complexity of the issues. But often in evaluating risk and balancing the cost/benefit equation, we have formulated our standards for exposure in terms of a young human male. A major sector of our population in which there are marked excursions from the average values is amongst the elderly. Changes in physiology have been documented; for example, disturbances in hormonal modulation, carbohydrate and lipid metabolism, and drug metabolism. This respectable, although spotty, literature on variability in older people cannot be ignored in risk assessment analyses. Indeed with the dramatic growth in numbers of this segment of our population, and with changes in mandatory retirement age allowing more older people to remain in the workforce, there is an urgent need to expand our knowledge of their variability. Our meeting, for the first time, will bring together knowledge of human heterogeneity as a coherent whole to consider how the introduction of this new factor might affect risk assessment analyses. We have invited presentations from recognized experts from the fields of gerontology, epidemiology, genetics, carcinogenesis and teratology. Our discussions will demonstrate the extent of variation in "normal" populations, and reduce scientific uncertainties. Since the resolution and obligations of risk assessment are, in the last analysis, a political process, we also shall involve experts from the regulatory agencies so that the scientific and political risk analysis processes go hand-in-hand.